Field of the Invention
The present invention relates to a thin film transistor array and a manufacturing method of the same.
Discussion of the Background
Due to the remarkable development of information technology, nowadays, information is frequently transmitted and received with laptop computers or portable information terminals. It is common knowledge that a ubiquitous society enabling information to be exchanged anywhere will be attained in the near future. In such a society, a lighter and slim information terminal is desirable.
Currently, as a semiconductor material, silicon based materials are mainly employed and, as a manufacturing method, photolithography is generally used.
In recent years, printable electronics in which an electrical component is manufactured by using a printing technique are attracting attention. By using the printing technique, the following advantages can be attained, that is, equipment cost and manufacturing cost are reduced compared to using the photolithography and, since a vacuum and high temperature environment are not necessary, a plastic substrate can be used. The printing process efficiently utilizes materials and does not require a development process and an etching process, producing a smaller amount of waste liquid. Accordingly, the environmental load caused by the printing method can be kept low.
On the other hand, the printing process is likely to have low pattern definition and low alignment accuracy compared to the photolithography. In particular, in the case where a thick film having a thickness of the order of several micrometers is required, screen printing is often used. However, a high definition pattern is difficult to form because of fluidity of paste.
As a printing method having resolution higher than that of screen printing, a gravure offset printing can be used (e.g., PTL 1).
In the gravure offset printing, a pattern is formed via a silicone blanket. When the paste is transferred onto the silicone blanket from an intaglio, solvent is absorbed by the blanket to lower the fluidity. As a result, the resolution is improved.
However, in the case where a pattern-formed region is wider than a non-formed region such as in an interlayer insulation film pattern, the amount of solvent absorbed by the silicone blanket increases, causing a change in the time taken for lowering the fluidity and lowering of the alignment accuracy due to swelling of the blanket. Also, when forming a pattern having via holes penetrating therethrough, a doctoring is applied, by a blade, to an intaglio in which protrusions are formed corresponding to the via holes. Therefore, there is a concern that the blade may be bent due to a small number of contacts between the intaglio and the blade, and the protrusions may be chipped when the blade contacts the discontinuous protrusions.
PTL1: JP-A-2011-37999